Carboxyl group-containing polymers are useful polymers used in various industrial fields and are useful specifically for use in aqueous environment (e.g. dispersants, detergent compositions).
An example of conventional carboxyl group-containing polymers is a hydrophobic group-containing copolymer that includes a structure unit (a) derived from a ether bond-containing monomer (A) at a level of from 1 to 49% by mass, a structure unit (b) derived from a carboxylic group-containing monomer (B) at a level of from 50 to 98% by mass, and a structure unit (d) derived from a sulfonic acid group-containing monomer (D) at a level of from 1 to 49% by mass based on 100% by mass of all the structure units derived from all the monomers (Patent Literature 1). Patent Literature 1 states that this hydrophobic group-containing copolymer has an excellent capacity to reduce/prevent precipitation of surfactants enough, and therefore effectively prevents surfactants from precipitating when used in a detergent composition or the like.